Transesophageal echocardiography and diagnostic cardiac catheterization were performed in 36 patients with symptomatic mitral stenosis to assess the incidence and significance of systolic flow reversal in the pulmonary veins. Mitral regurgitation was graded by contrast ventriculography, and left atrial pressure was directly measured after transseptal puncture. Pulmonary venous flow was recorded with transesophageal Doppler imaging from the left upper pulmonary vein. Early systolic flow reversal was identified in 11 patients (31%) and began an average of 58 +/- 13 ms after QRS onset. This pattern correlated strongly with the presence of atrial fibrillation or flutter. Late systolic flow reversal was identified in 8 patients (22%), beginning an average of 245 +/- 46 ms after the QRS complex. These patients had higher left atrial V-wave pressure (36 +/- 10 vs 29 +/- 8 mm Hg; p < 0.05) and V-wave peak-X-descent trough (18 +/- 7 vs 11 +/- 5 mm Hg; p < 0.01) than patients without systolic flow reversal. Neither pattern of pulmonary venous flow reversal was related to the severity of angiographic mitral regurgitation. Systolic reversal of pulmonary venous flow is not specific for angiographically severe mitral regurgitation in patients with mitral stenosis. Similar limitations to pulmonary venous flow analysis likely apply to other patient groups with elevated left atrial pressure and poor left atrial compliance.